How do you interpret and report the results of ultrasonic testing for plant maintenance?

1 Know the basics of UT

UT works by sending a pulse of sound into the material and receiving the echoes that reflect from the boundaries or discontinuities. The time, amplitude, and shape of the echoes can indicate the location, size, and type of the defect. You need a UT device, a transducer, a couplant, and a display to perform UT. The transducer converts electrical energy into sound waves and vice versa. The couplant is a liquid or gel that helps the sound waves travel from the transducer to the material. The display shows the waveform or the signal of the echoes.

2 Choose the right method and settings

There are different methods of UT depending on the purpose and the configuration of the test. For example, pulse-echo method is used to measure the thickness of a material or detect internal flaws. Transmission method is used to check the integrity of a weld or a joint. Angle beam method is used to inspect curved or irregular surfaces. You also need to select the appropriate frequency, gain, and range of the sound waves depending on the material, geometry, and defect characteristics. Higher frequency provides better resolution but less penetration. Higher gain amplifies the signal but also increases the noise. Higher range covers more distance but reduces the accuracy.

3 Calibrate and scan the test area

Before you start testing, you need to calibrate the UT device using a standard reference block or a known defect. This ensures that the device is working properly and that the results are reliable. You also need to prepare the test area by cleaning and smoothing the surface, applying the couplant, and marking the scan lines or points. Then, you need to scan the test area by moving the transducer along the surface or placing it at different angles or positions. You need to follow a consistent and systematic pattern to cover the entire area and avoid missing any defects.

4 Analyze and interpret the waveform

As you scan the test area, you need to observe and analyze the waveform on the display. The waveform shows the amplitude and the time of flight of the echoes. The amplitude indicates the strength of the reflection and the time of flight indicates the distance of the reflector from the transducer. You need to compare the waveform with the baseline or the expected signal from a defect-free material. You also need to use some criteria or standards to identify and classify the defects. For example, you can use the 6 dB drop method to estimate the size of a defect by measuring the width of the echo at half of its peak amplitude.

5 Report and document the results

After you finish testing, you need to report and document the results of UT for plant maintenance. You need to include the following information in your report: the test method and parameters, the test area and location, the calibration data, the waveform images, the defect description and classification, the defect size and location, and any recommendations or actions. You also need to follow any specific formats or guidelines required by your organization or industry. You need to keep your report clear, concise, and accurate.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?